144 lines
3.3 KiB
C
144 lines
3.3 KiB
C
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#include "common.h"
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//#link "common.c"
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#include "rasterirq.h"
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//#link "rasterirq.ca65"
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#include "bcd.h"
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//#link "bcd.c"
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///// DEFINES
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#define GAME_BASE 0x400 // scrolling screen ram
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#define SCORE_BASE 0x2c00 // scoreboard screen ram
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#define SCROLL_TOP 8 // scroll top row
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#define SCROLL_ROWS 14 // scroll # of rows
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#define GROUND_ROW 7 // ground row (+ top row)
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///// VARIABLES
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word scroll_x = 0; // current scroll X position
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word score = 0; // current player score
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///// FUNCTIONS
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// display list used by rasterirq.h
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// draws scoreboard and sets scroll register
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void display_list() {
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// set x scroll register to scroll value
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SET_SCROLL_X(scroll_x);
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// set background color
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VIC.bgcolor[0] = COLOR_CYAN;
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// next interrupt is two rows from bottom
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DLIST_NEXT(250-16);
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// set background color
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VIC.bgcolor[0] = COLOR_BLUE;
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// screen memory = 0x2800
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SET_VIC_SCREEN(SCORE_BASE);
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// clear x scroll register
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SET_SCROLL_X(0);
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// next interrupt is bottom of frame
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DLIST_NEXT(250);
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// reset screen to 0x400
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SET_VIC_SCREEN(0x400);
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// next interrupt is above top of next frame
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DLIST_RESTART(40);
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}
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void update_scoreboard() {
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draw_bcd_word(SCRNADR(SCORE_BASE,7,24), score);
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}
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void add_score(int delta) {
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score = bcd_add(score, delta);
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}
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// clear scoreboard and draw initial strings
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void init_scoreboard() {
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memset((void*)SCORE_BASE, ' ', 1024);
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memcpy((void*)SCRNADR(SCORE_BASE,1,24), "SCORE:", 6);
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update_scoreboard();
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}
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byte get_char_for_row(byte row) {
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// ground?
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if (row >= GROUND_ROW) { return 253; }
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// obstacle?
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if (row >= GROUND_ROW-3) {
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// only show obstacle for certain values of scroll_x
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if ((scroll_x & 0b1110000) == 0) { return 247; }
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}
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// default is the sky (empty space)
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return 32;
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}
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void draw_right_column() {
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// get the top-right corner address of scroll area
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word addr = SCRNADR(GAME_BASE, 39, SCROLL_TOP);
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byte row;
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// draw one character per row
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for (row=0; row<SCROLL_ROWS; row++) {
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POKE(addr, get_char_for_row(row));
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addr += 40;
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}
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}
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void scroll_one_column_left() {
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// copy several rows of screen memory
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// backwards one byte
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const word start = SCRNADR(GAME_BASE, 0, SCROLL_TOP);
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const word nbytes = SCROLL_ROWS*40-1;
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memcpy((byte*)start, (byte*)start+1, nbytes);
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// draw the right column of characters
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draw_right_column();
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}
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void scroll_one_pixel_left() {
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// scroll left one pixel
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scroll_x -= 1;
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// set scroll register with lower three bits
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VIC.ctrl2 = (VIC.ctrl2 & ~7) | (scroll_x & 7);
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// move screen memory if the scroll register
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// has just gone past 0 and wrapped to 7
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if ((scroll_x & 7) == 7) {
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scroll_one_column_left();
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}
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}
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void main() {
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// clear screen, set background color
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clrscr();
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VIC.bgcolor[0] = COLOR_CYAN;
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VIC.bordercolor = COLOR_BLUE;
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// set vertical scroll = 3, 25 rows
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VIC.ctrl1 = 0b00011011;
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// set 38 column mode (for X scrolling)
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VIC.ctrl2 = 0b00000000;
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// set uniform color of characters
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memset(COLOR_RAM, COLOR_WHITE, 1000);
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// setup scoreboard
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init_scoreboard();
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// setup rasterirq library for scoreboard split
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DLIST_SETUP(display_list);
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// game loop, repeat forever
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while (1) {
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// wait for end of frame
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waitvsync();
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// scroll screen
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scroll_one_pixel_left();
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// add to score
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add_score(0x0001);
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update_scoreboard();
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}
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}
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